The invention relates to an operating mechanism of an electrical switchgear device, especially a multipole circuit breaker or a fuse-switch incorporated in an electrical distribution cubicle, connected by means of connecting cables, the movable assembly of the circuit breaker being able to occupy three distinct stable positions, namely a first position in which the contacts are closed, a second intermediate position in which the contacts are open, and a third earthed position in which the outgoing cables are electrically earthed by means of the movable contacts of the corresponding phases, the kinematic transmission system of said mechanism comprising:
an elastic energy storage system associated with a rotary transmission device securedly united to the movable assembly,
operating means operating in conjunction with the energy storage system to actuate the transmission device in one of the three positions, earthing being accomplished from the second intermediate position O,
and blocking means of the transmission device in each of the three positions of the circuit breaker.
A mechanism of the kind mentioned is described in French Pat. No. 2,500,222 and comprises a single spring associated with a toggle-joint and an operating crank. A tumbler-type mechanism of this kind is perfectly suited to switches having average breaking performances, but is not suitable for switchgear with higher performances, notably circuit breakers.